This invention refers to a hermetic compressor for small refrigerating machines and, more particularly, to a new constructive solution for a discharge and suction reed valve in a hermetic compressor of rotating type rolling piston type or reciprocating piston type.
The construction of a discharge system in hermetic compressors, especially in those of the rotary rolling piston type directly affects compressor energy and volume losses. One of the losses is the energy loss due to overpressure related to the readiness of opening the outlet valve after the pressure within the cylinder compression chamber has reached the discharge pressure. Another is a relatively poor efficiency of the discharge system, which once open, must operate as quickly as possible to evacuate the gas to be discharged.
In cases where the outlet valve does not adequately open, a condition of overpressure inside the cylinder compression will occur and the longer is the part of the compression cycle during said overpressure condition, the higher will be the effort and the power loss that the compressor crankshaft will have to overcome. As discussed above, it can be said that the careful definition of the constructive characteristics for the discharge system is a very important part when sizing a hermetic compressor.
The more usual solution adopted for the hermetic compressor discharge system, especially those of rotating rolling piston type, is a blade valve (or reed valve) whose stem is attached through screws or rivets to the plate in which the cylinder discharge hole is made.
A reed valve as above describes has some operating drawbacks causing energy losses in the compressor. Known reed valves have their stem attached by a rivet or screw in such way that the blade attachment is at the same level of its seat on the discharge hole. The known reed valves open at an angle (not parallel) to the seat, thus producing asymmetry in the discharge flow, making it inefficient. The above discussed operating characteristics for reed valves impair the gas discharge flow from the cylinder compression chamber thereby increasing the energy loss due to overpressure.
The above mentioned disadvantages concerning the known discharge valve in the form of a blade for rotary and reciprocating hermetic compressors can also be associated with suction valves in the form of reed valves for alternate hermetic compressors.